Effects of human full-length amelogenin on the proliferation of human mesenchymal stem cells derived from bone marrow

Regeneration of injured articular cartilage using the recombinant human amelogenin protein

Aims

Cartilage injuries rarely heal spontaneously and often require surgical intervention, leading to the formation of biomechanically inferior fibrous tissue. This study aimed to evaluate the possible effect of amelogenin on the healing process of a large osteochondral injury (OCI) in a rat model.

Methods

A reproducible large OCI was created in the right leg femoral trochlea of 93 rats. The OCIs were treated with 0.1, 0.5, 1.0, 2.5, or 5.0 μg/μl recombinant human amelogenin protein (rHAM+) dissolved in propylene glycol alginate (PGA) carrier, or with PGA carrier alone. The degree of healing was evaluated 12 weeks after treatment by morphometric analysis and histological evaluation. Cell recruitment to the site of injury as well as the origin of the migrating cells were assessed four days after treatment with 0.5 μg/μl rHAM+ using immunohistochemistry and immunofluorescence.

Results

A total of 12 weeks after treatment, 0.5 μg/μl rHAM+ brought about significant repair of the subchondral bone and cartilage. Increased expression of proteoglycan and type II collagen and decreased expression of type I collagen were revealed at the surface of the defect, and an elevated level of type X collagen at the newly developed tide mark region. Conversely, the control group showed osteoarthritic alterations. Recruitment of cells expressing the mesenchymal stem cell (MSC) markers CD105 and STRO-1, from adjacent bone marrow toward the OCI, was noted four days after treatment.

Conclusion

We found that 0.5 μg/μl rHAM+ induced in vivo healing of injured articular cartilage and subchondral bone in a rat model, preventing the destructive post-traumatic osteoarthritic changes seen in control OCIs, through paracrine recruitment of cells a few days after treatment.

Amelogenin-Derived Peptides in Bone Regeneration: A Systematic Review

Amelogenins are enamel matrix proteins currently used to treat bone defects in periodontal surgery. Recent studies have highlighted the relevance of amelogenin-derived peptides, named LRAP, TRAP, SP, and C11, in bone tissue engineering. Interestingly, these peptides seem to maintain or even improve the biological activity of the full-length protein, which has received attention in the field of bone regeneration. In this article, the authors combined a systematic and a narrative review. The former is focused on the existing scientific evidence on LRAP, TRAP, SP, and C11's ability to induce the production of mineralized extracellular matrix, while the latter is concentrated on the structure and function of amelogenin and amelogenin-derived peptides. Overall, the collected data suggest that LRAP and SP are able to induce stromal stem cell differentiation towards osteoblastic phenotypes; specifically, SP seems to be more reliable in bone regenerative approaches due to its osteoinduction and the absence of immunogenicity. However, even if some evidence is convincing, the limited number of studies and the scarcity of in vivo studies force us to wait for further investigations before drawing a solid final statement on the real potential of amelogenin-derived peptides in bone tissue engineering.

Lysosomal protein surface expression discriminates fat- from bone-forming human mesenchymal precursor cells

Tissue resident mesenchymal stem/stromal cells (MSCs) occupy perivascular spaces. Profiling human adipose perivascular mesenchyme with antibody arrays identified 16 novel surface antigens, including endolysosomal protein CD107a. Surface CD107a expression segregates MSCs into functionally distinct subsets. In culture, CD107alow cells demonstrate high colony formation, osteoprogenitor cell frequency, and osteogenic potential. Conversely, CD107ahigh cells include almost exclusively adipocyte progenitor cells. Accordingly, human CD107alow cells drove dramatic bone formation after intramuscular transplantation in mice, and induced spine fusion in rats, whereas CD107ahigh cells did not. CD107a protein trafficking to the cell surface is associated with exocytosis during early adipogenic differentiation. RNA sequencing also suggested that CD107alow cells are precursors of CD107ahigh cells. These results document the molecular and functional diversity of perivascular regenerative cells, and show that relocation to cell surface of a lysosomal protein marks the transition from osteo- to adipogenic potential in native human MSCs, a population of substantial therapeutic interest.

Effects of enamel matrix proteins on adherence, proliferation and migration of epithelial cells: A real-time in vitro study

Enamel matrix derivative (EMD) can mimic odontogenic effects by inducing the proliferation and differentiation of connective tissue progenitor cells, stimulating bone growth and arresting epithelial cells migration. To the best of our knowledge, there is no data indicating that any active component of EMD reduces epithelial cell viability. The present study examines the impact of commercial lyophilized EMD, porcine recombinant amelogenin (prAMEL; 21.3 kDa) and tyrosine-rich amelogenin peptide (TRAP) on the adherence, proliferation and migration of human epithelial cells in real-time. The tongue carcinoma cell line SCC-25 was stimulated with EMD, porcine recombinant AMEL and TRAP, at concentrations of 12.5, 25 and 50 µg/ml. Cell adherence, migration and proliferation were monitored in real-time using the xCELLigence system. No significant effects of EMD on the morphology, adhesion, proliferation and migration of SCC-25 cells were observed. However, porcine recombinant AMEL had a dose-dependent inhibitory effect on SCC-25 cell proliferation and migration. Predominantly, no notable differences were found between control and TRAP-treated cells in terms of cell adhesion and migration, a decrease in proliferation was observed, but this was not statistically significant. EMD and its active components do not increase the tongue cancer cell viability.

Skeletal ligament healing using the recombinant human amelogenin protein

Injuries to ligaments are common, painful and debilitating, causing joint instability and impaired protective proprioception sensation around the joint. Healing of torn ligaments usually fails to take place, and surgical replacement or reconstruction is required. Previously, we showed that in vivo application of the recombinant human amelogenin protein (rHAM⁺) resulted in enhanced healing of the tooth‐supporting tissues. The aim of this study was to evaluate whether amelogenin might also enhance repair of skeletal ligaments. The rat knee medial collateral ligament (MCL) was chosen to prove the concept. Full thickness tear was created and various concentrations of rHAM⁺, dissolved in propylene glycol alginate (PGA) carrier, were applied to the transected MCL. 12 weeks after transection, the mechanical properties, structure and composition of transected ligaments treated with 0.5 μg/μl rHAM⁺ were similar to the normal un‐transected ligaments, and were much stronger, stiffer and organized than control ligaments, treated with PGA only. Furthermore, the proprioceptive free nerve endings, in the 0.5 μg/μl rHAM⁺ treated group, were parallel to the collagen fibres similar to their arrangement in normal ligament, while in the control ligaments the free nerve endings were entrapped in the scar tissue at different directions, not parallel to the axis of the force. Four days after transection, treatment with 0.5 μg/μl rHAM⁺ increased the amount of cells expressing mesenchymal stem cell markers at the injured site. In conclusion application of rHAM⁺ dose dependently induced mechanical, structural and sensory healing of torn skeletal ligament. Initially the process involved recruitment and proliferation of cells expressing mesenchymal stem cell markers.

Full-length amelogenin influences the differentiation of human dental pulp stem cells

Background

Amelogenin is an extracellular matrix protein well known for its role in the organization and mineralization of enamel. Clinically, it is used for periodontal regeneration and, due to its finding also in predentin and intercellular spaces of dental pulp cells, it has recently been suggested for pulp capping procedures. The aim of this study was to analyse in vitro the effect of the recombinant human full-length amelogenin on the growth and differentiation of human dental pulp stem cells (hDPSCs).

Methods

Human DPSCs were treated with a supplement of amelogenin at a concentration of 10 ng/ml, 100 ng/ml and 1000 ng/ml. The groups were compared to the unstimulated control in terms of cell morphology and proliferation, mineralization and gene expression for ALP (alkaline phosphatase), DMP1 (dentin matrix protein-1) and DSPP (dentin sialophosphoprotein).

Results

Amelogenin affects hDPSCs differently than PDL (periodontal ligament) cells and other cell lines. The proliferation rate at two weeks is significantly reduced in presence of the highest concentration of amelogenin as compared to the unstimulated control. hDPSCs treated with low concentrations present a downregulation of DMP1 and DSPP, which is significant for DSPP (p = 0.011), but not for DMP1 (p = 0.395).

Conclusions

These finding suggest that the role of full-length amelogenin is not restricted to participation in tooth structure. It influences the differentiation of hDPSC according to various concentrations and this might impair the clinical results of pulp capping.

Human bone marrow stromal cell confluence: effects on cell characteristics and methods of assessment

BACKGROUND AIMS

Ex vivo expansion and serial passage of human bone marrow stromal cells (BMSCs, also known as bone marrow-derived mesenchymal stem cells) is required to obtain sufficient quantities for clinical therapy. The BMSC confluence criteria used to determine passage and harvest timing vary widely, and the impact of confluence on BMSC properties remains controversial. The effects of confluence on BMSC properties were studied and confluence-associated markers were identified.

METHODS

BMSC characteristics were analyzed as they grew from 50% to 100% confluence, including viability, population doubling time, apoptosis, colony formation, immunosuppression, surface marker expression, global gene expression and microRNA expression. In addition, culture supernatant protein, glucose, lactate and pH levels were analyzed.

RESULTS

Confluence-dependent changes were detected in the expression of several cell surface markers: 39 culture supernatant proteins, 26 microRNAs and 2078 genes. Many of these surface markers, proteins, microRNAs and genes have been reported to be important in BMSC function. The pigment epithelium-derived factor/vascular endothelial growth factor ratio increased with confluence, but 80% and 100% confluent BMSCs demonstrated a similar level of immunosuppression of mixed lymphocyte reactions. In addition, changes in lactate and glucose levels correlated with BMSC density.

CONCLUSIONS

BMSC characteristics change as confluence increases. 100% confluent BMSCs may have compromised pro-angiogenesis properties but may retain their immunomodulatory properties. Supernatant lactate and glucose levels can be used to estimate confluence and ensure consistency in passage and harvest timing. Flow cytometry or microRNA expression can be used to confirm that the BMSCs have been harvested at the appropriate confluence.

The effects of synthetic oligopeptide derived from enamel matrix derivative on cell proliferation and osteoblastic differentiation of human mesenchymal stem cells

Enamel matrix derivative (EMD) is widely used in periodontal tissue regeneration therapy. However, because the bioactivity of EMD varies from batch to batch, and the use of a synthetic peptide could avoid use from an animal source, a completely synthetic peptide (SP) containing the active component of EMD would be useful. In this study an oligopeptide synthesized derived from EMD was evaluated for whether it contributes to periodontal tissue regeneration. We investigated the effects of the SP on cell proliferation and osteoblast differentiation of human mesenchymal stem cells (MSCs), which are involved in tissue regeneration. MSCs were treated with SP (0 to 1000 ng/mL), to determine the optimal concentration. We examined the effects of SP on cell proliferation and osteoblastic differentiation indicators such as alkaline phosphatase activity, the production of procollagen type 1 C-peptide and osteocalcin, and on mineralization. Additionally, we investigated the role of extracellular signal-related kinases (ERK) in cell proliferation and osteoblastic differentiation induced by SP. Our results suggest that SP promotes these processes in human MSCs, and that ERK inhibitors suppress these effects. In conclusion, SP promotes cell proliferation and osteoblastic differentiation of human MSCs, probably through the ERK pathway.

Tracking endogenous amelogenin and ameloblastin in vivo

Research on enamel matrix proteins (EMPs) is centered on understanding their role in enamel biomineralization and their bioactivity for tissue engineering. While therapeutic application of EMPs has been widely documented, their expression and biological function in non-enamel tissues is unclear. Our first aim was to screen for amelogenin (AMELX) and ameloblastin (AMBN) gene expression in mandibular bones and soft tissues isolated from adult mice (15 weeks old). Using RT-PCR, we showed mRNA expression of AMELX and AMBN in mandibular alveolar and basal bones and, at low levels, in several soft tissues; eyes and ovaries were RNA-positive for AMELX and eyes, tongues and testicles for AMBN. Moreover, in mandibular tissues AMELX and AMBN mRNA levels varied according to two parameters: 1) ontogenic stage (decreasing with age), and 2) tissue-type (e.g. higher level in dental epithelial cells and alveolar bone when compared to basal bone and dental mesenchymal cells in 1 week old mice). In situ hybridization and immunohistodetection were performed in mandibular tissues using AMELX KO mice as controls. We identified AMELX-producing (RNA-positive) cells lining the adjacent alveolar bone and AMBN and AMELX proteins in the microenvironment surrounding EMPs-producing cells. Western blotting of proteins extracted by non-dissociative means revealed that AMELX and AMBN are not exclusive to mineralized matrix; they are present to some degree in a solubilized state in mandibular bone and presumably have some capacity to diffuse. Our data support the notion that AMELX and AMBN may function as growth factor-like molecules solubilized in the aqueous microenvironment. In jaws, they might play some role in bone physiology through autocrine/paracrine pathways, particularly during development and stress-induced remodeling.

Expression and function of enamel-related gene products in calvarial development

Enamel-related gene products (ERPs) are detected in non-enamel tissues such as bone. We hypothesized that, if functional, ERP expression corresponds with distinct events during osteoblast differentiation and affects bone development and mineralization. In mouse calvariae and MC3T3 cells, expression profiles of enamel-related gene products (ERPs) correlated with key events in post-natal calvarial development and MC3T3 cell mineralization. Developing skulls from both Amel- and Ambn-deficient animals were approximately 15% shorter when compared with those of wild-type controls, and their sutures remained patent for a longer period of time. Analysis of Amel- and Ambn-deficient calvariae and calvarial osteoblast cultures revealed a dramatic reduction in mineralized nodules, a significant reduction in Runx2, Sp7, Ibsp, and Msx2 expression, and a reduction in Alx4 in Amel-deficient calvariae vs. an increase in Alx4 in Ambn-deficient calvariae. Analysis of these data indicates that ERP expression follows defined developmental profiles and affects osteoblast differentiation, mineralization, and calvarial bone development. We propose that, in parallel to their role in the developing enamel matrix, ERPs have retained an evolutionary conserved function related to the biomineralization of bones.

Craniofacial bone tissue engineering

There are numerous conditions, such as trauma, cancer, congenital malformations, and progressive deforming skeletal diseases, that can compromise the function and architectonics of bones of craniofacial region. The need to develop new approaches for treatment of these disorders arises from the fact that conventional therapeutic strategies face many obstacles and limitations. The use of tissue engineering in regeneration of craniofacial bone structures is a very promising possibility and a great challenge for researchers and practitioners. Developments in stem cell biology and engineering have led to the discovery of different stem cell populations and biodegradable materials with suitable properties. This review summarizes the current achievements in tissue engineering of craniofacial bone, temporomandibular joint, and periodontal ligament.

Qualitative and quantitative evaluation of Simon™, a new CE-based automated Western blot system as applied to vaccine development

Many CE-based technologies such as imaged capillary IEF, CE-SDS, CZE, and MEKC are well established for analyzing proteins, viruses, or other biomolecules such as polysaccharides. For example, imaged capillary isoelectric focusing (charge-based protein separation) and CE-SDS (size-based protein separation) are standard replacement methods in biopharmaceutical industries for tedious and labor intensive IEF and SDS-PAGE methods, respectively. Another important analytical tool for protein characterization is a Western blot, where after size-based separation in SDS-PAGE the proteins are transferred to a membrane and blotted with specific monoclonal or polyclonal antibodies. Western blotting analysis is applied in many areas such as biomarker research, therapeutic target identification, and vaccine development. Currently, the procedure is very manual, laborious, and time consuming. Here, we evaluate a new technology called Simple Western™ (or Simon™) for performing automated Western analysis. This new technology is based on CE-SDS where the separated proteins are attached to the wall of capillary by a proprietary photo activated chemical crosslink. Subsequent blotting is done automatically by incubating and washing the capillary with primary and secondary antibodies conjugated with horseradish peroxidase and detected with chemiluminescence. Typically, Western blots are not quantitative, hence we also evaluated the quantitative aspect of this new technology. We demonstrate that Simon™ can quantitate specific components in one of our vaccine candidates and it provides good reproducibility and intermediate precision with CV <10%.

Analogous effects of recombinant human full-length amelogenin expressed by Pichia pastoris yeast and enamel matrix derivative in vitro

OBJECTIVES

Amelogenins are proposed to be responsible for enamel matrix derivative (EMD)-induced periodontal regeneration; however, heterogeneity of amelogenins makes it challenging to purify the full-length proteins. This study has been carried out to express and purify a recombinant full-length human amelogenin protein (rHhAm175) in the eukaryotic yeast Pichia pastoris, and further compare biological responses of human periodontal ligament fibroblasts (PDLFs) to rHhAm175 and porcine EMD (pEMD).

MATERIALS AND METHODS

Human cDNA encoding a 175-amino acid amelogenin was subcloned into the pPIC3.5K vector. The rHhAm175 expressed in P. pastoris GS115 (Mut+) was purified and characterized. We examined cell attachment, migration and proliferation responses of human PDLFs to rHhAm175 and pEMD respectively, and characterized associated changes of proliferation-related intracellular signalling molecules, including extracellular signal response kinase (ERK) and Akt kinases/protein kinase B (Akt/PKB) kinases.

RESULTS

The purified rHhAm175 was confirmed to be molecular mass 22 021.13 Da, phosphorylated human amelogenin, and alone significantly promoted proliferation and migration of human PDLFs to an extent comparable to that of pEMD. Cell attachment was increased over the first 60 min incubation with rHhAm175 or pEMD. Both rHhAm175 and pEMD induced PDLF mitogenesis via extracellular signal response kinase (ERK1/2), but not by Akt kinases/protein kinase B (Akt/PKB).

CONCLUSIONS

rHhAm175 modulated cell activities of human PDLFs, to a comparable extent as porcine EMD. These data suggest that rHhAm175 might be used to induce periodontal tissue regeneration.

The inhibitory effects of m-nisoldipine on the 5-hydroxytryptamine-induced proliferation of pulmonary artery smooth muscle cells via Ca2+ antagonism and antioxidant mechanisms

The excessive proliferation of pulmonary artery smooth muscle cells (PASMCs) plays a critical role in the development of pulmonary arterial hypertension. Recent studies indicate that Ca(2+) and reactive oxygen species are critically involved in the process of smooth muscle cell proliferation stimulated by mitogens, such as 5-hydroxytryptamine (5-HT). Because m-nisoldipine, a Ca(2+) channel blocker of the dihydropyridine class, possesses some calcium antagonistic and antioxidant properties, we investigated the effect of m-nisoldipine on PASMC proliferation. The results indicated that m-nisoldipine inhibited 5-HT-induced PASMC proliferation, evaluated by BrdU incorporation and the MTT assay, and this effect was associated with a decreased expression of proliferating cell nuclear antigen (PCNA). Flow cytometry analysis showed that m-nisoldipine blocked 5-HT-induced cell-cycle progression by arresting the cells in the G(0)/G(1) phase. Next, the production of reactive oxygen species and the levels of [Ca(2+)](i) in PASMCs were measured by laser scanning confocal microscopy; m-nisoldipine pretreatment attenuated the [Ca(2+)](i) elevation and the production of reactive oxygen species induced by 5-HT. In addition, m-nisoldipine significantly decreased the 5-HT-induced activation of extracellular signal-regulated kinase (ERK1/2) and c-Jun N-terminal kinase (JNK) and the subsequent c-fos and c-jun mRNA expression. Meanwhile, results also showed that N-acetylcysteine (a reactive oxygen species scavenger) suppressed the proliferation and the ERK1/2 and JNK activation induced by 5-HT. In summary, this study demonstrated that m-nisoldipine effectively suppressed the 5-HT-induced PASMC proliferation, ERK1/2 and JNK activation and subsequent c-fos and c-jun mRNA expression, all of which might be associated with the Ca(2+) antagonistic and antioxidant properties of m-nisoldipine.

Enamel matrix derivative: a review of cellular effects in vitro and a model of molecular arrangement and functioning

BACKGROUND

Enamel matrix derivative (EMD), the active component of Emdogain®, is a viable option in the treatment of periodontal disease owing to its ability to regenerate lost tissue. It is believed to mimic odontogenesis, though the details of its functioning remain the focus of current research.

OBJECTIVE

The aim of this article is to review all relevant literature reporting on the composition/characterization of EMD as well as the effects of EMD, and its components amelogenin and ameloblastin, on the behavior of various cell types in vitro. In this way, insight into the underlying mechanism of regeneration will be garnered and utilized to propose a model for the molecular arrangement and functioning of EMD.

METHODS

A review of in vitro studies of EMD, or components of EMD, was performed using key words "enamel matrix proteins" OR "EMD" OR "Emdogain" OR "amelogenin" OR "ameloblastin" OR "sheath proteins" AND "cells." Results of this analysis, together with current knowledge on the molecular composition of EMD and the structure and regulation of its components, are then used to present a model of EMD functioning.

RESULTS

Characterization of the molecular composition of EMD confirmed that amelogenin proteins, including their enzymatically cleaved and alternatively spliced fragments, dominate the protein complex (>90%). A small presence of ameloblastin has also been reported. Analysis of the effects of EMD indicated that gene expression, protein production, proliferation, and differentiation of various cell types are affected and often enhanced by EMD, particularly for periodontal ligament and osteoblastic cell types. EMD also stimulated angiogenesis. In contrast, EMD had a cytostatic effect on epithelial cells. Full-length amelogenin elicited similar effects to EMD, though to a lesser extent. Both the leucine-rich amelogenin peptide and the ameloblastin peptides demonstrated osteogenic effects. A model for molecular structure and functioning of EMD involving nanosphere formation, aggregation, and dissolution is presented.

CONCLUSIONS

EMD elicits a regenerative response in periodontal tissues that is only partly replicated by amelogenin or ameloblastin components. A synergistic effect among the various proteins and with the cells, as well as a temporal effect, may prove important aspects of the EMD response in vivo.

Chondrogenic potential of stem cells derived from amniotic fluid, adipose tissue, or bone marrow encapsulated in fibrin gels containing TGF-β3

In this study, several types of hMSCs, derived from bone marrow, adipose tissue, or amniotic fluid, were encapsulated in a fibrin hydrogel mixed with TGF-β3 and then evaluated for their capacity for differentiation in vitro and in vivo. For determination of stem cell differentiation, RT-PCR, real time quantitative PCR (qPCR), histology, and immunohistochemical assays were used for analysis of chondrogenesis. Using these analysis methods, several of the cultured hMSCS were found to highly express genes and proteins specific to cartilage forming tissues. Additionally, similar trends in expression were found in tissue recovered from nude mice transplanted with several types of hMSCs encapsulated in a fibrin hydrogel containing TGF-β3. The results of both in vitro and in vivo analyses showed that cultured or transplanted hMSCs mixed with TGF-β3 in a fibrin hydrogel differentiated into chondrocytes, suggesting that these cells would be suitable for reconstruction of hyaline articular cartilage.

Premature osteoblast clustering by enamel matrix proteins induces osteoblast differentiation through up-regulation of connexin 43 and N-cadherin

In recent years, enamel matrix derivative (EMD) has garnered much interest in the dental field for its apparent bioactivity that stimulates regeneration of periodontal tissues including periodontal ligament, cementum and alveolar bone. Despite its widespread use, the underlying cellular mechanisms remain unclear and an understanding of its biological interactions could identify new strategies for tissue engineering. Previous in vitro research has demonstrated that EMD promotes premature osteoblast clustering at early time points. The aim of the present study was to evaluate the influence of cell clustering on vital osteoblast cell-cell communication and adhesion molecules, connexin 43 (cx43) and N-cadherin (N-cad) as assessed by immunofluorescence imaging, real-time PCR and Western blot analysis. In addition, differentiation markers of osteoblasts were quantified using alkaline phosphatase, osteocalcin and von Kossa staining. EMD significantly increased the expression of connexin 43 and N-cadherin at early time points ranging from 2 to 5 days. Protein expression was localized to cell membranes when compared to control groups. Alkaline phosphatase activity was also significantly increased on EMD-coated samples at 3, 5 and 7 days post seeding. Interestingly, higher activity was localized to cell cluster regions. There was a 3 fold increase in osteocalcin and bone sialoprotein mRNA levels for osteoblasts cultured on EMD-coated culture dishes. Moreover, EMD significantly increased extracellular mineral deposition in cell clusters as assessed through von Kossa staining at 5, 7, 10 and 14 days post seeding. We conclude that EMD up-regulates the expression of vital osteoblast cell-cell communication and adhesion molecules, which enhances the differentiation and mineralization activity of osteoblasts. These findings provide further support for the clinical evidence that EMD increases the speed and quality of new bone formation in vivo.

The role of cell surface markers and enamel matrix derivatives on human periodontal ligament mesenchymal progenitor responses in vitro

Periodontitis is a chronic-, infectious-disease of the human periodontium that is characterized by the loss of supporting tissues surrounding the tooth such as the periodontal ligament (PDL), cementum and alveolar bone. Regeneration of the periodontium is dependent on the participation of mesenchymal stem/stromal cells (MSC) resident in the PDL. Enamel matrix derivative (EMD), an extract from immature porcine enamel rich in amelogenin protein but that also contain bone morphogenetic protein (BMP), is used to treat periodontal defects. The effects of EMD on MSC cells of the PDL are not well characterized. In this in vitro study, we identify PDL progenitor cells from multiple individuals and demonstrate that EMD stimulates them. We show that the effect of EMD on cell proliferation and migration is mediated through the amelogenin it contains, while the differentiation of these progenitor cells to cell types of mineralized tissue is mainly due to BMP signaling.

The influence of Leucine-rich amelogenin peptide on MSC fate by inducing Wnt10b expression

Amelogenin is the most abundant protein of the enamel organic matrix and is a structural protein indispensable for enamel formation. One of the amelogenin splicing isoforms, Leucine-rich Amelogenin Peptide (LRAP) induces osteogenesis in various cell types. Previously, we demonstrated that LRAP activates the canonical Wnt signaling pathway to induce osteogenic differentiation of mouse ES cells through the concerted regulation of Wnt agonists and antagonists. There is a reciprocal relationship between osteogenic and adipogenic differentiation in bone marrow mesenchymal stem cells (BMMSCs). Wnt10b-mediated activation of canonical Wnt signaling has been shown to regulate mesenchymal stem cell fate. Using the bipotential bone marrow stromal cell line ST2, we have demonstrated that LRAP activates the canonical Wnt/β-catenin signaling pathway. A specific Wnt inhibitor sFRP-1 abolishes the effect of LRAP on the stimulation of osteogenesis and the inhibition of adipogenesis of ST2 cells. LRAP treatment elevates the Wnt10b expression level whereas Wnt10b knockdown by siRNA abrogates the effect of LRAP. We show here that LRAP promotes osteogenesis of mesenchymal stem cells at the expense of adipogenesis through upregulating Wnt10b expression to activate Wnt signaling.